After _gadget_stop_activity is executed, we can consider the hardware operation for gadget has finished, and the udc can be stopped and enter low power mode. So, any later hardware operations (from usb_ep_ops APIs or usb_gadget_ops APIs) should be considered invalid, any deinitializatons has been covered at _gadget_stop_activity.

I meet this problem when I plug out usb cable from PC using mass_storage gadget, my callstack like: vbus interrupt->.vbus_session-> composite_disconnect ->pm_runtime_put_sync(&_gadget->dev), the composite_disconnect will call fsg_disable, but fsg_disable calls usb_ep_disable using async way, there are register accesses for usb_ep_disable. So sometimes, I get system hang due to visit register without clock, sometimes not.

The Linux Kernel USB maintainer Alan Stern suggests this kinds of solution. See: http://marc.info/?l=linux-usb&m=138541769810983&w=2.

Cc: stable@vger.kernel.org #v4.9+ Signed-off-by: Peter Chen peter.chen@nxp.com --- This patch is at NXP internal tree long time, and no issues have found. Submit to mainline kenrel.

drivers/usb/chipidea/udc.c | 32 ++++++++++++++++++++++++-------- 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/drivers/usb/chipidea/udc.c b/drivers/usb/chipidea/udc.c index 053432d79bf7..8f18e7b6cadf 100644 --- a/drivers/usb/chipidea/udc.c +++ b/drivers/usb/chipidea/udc.c @@ -709,12 +709,6 @@ static int _gadget_stop_activity(struct usb_gadget *gadget) struct ci_hdrc *ci = container_of(gadget, struct ci_hdrc, gadget); unsigned long flags;

- spin_lock_irqsave(&ci->lock, flags); - ci->gadget.speed = USB_SPEED_UNKNOWN; - ci->remote_wakeup = 0; - ci->suspended = 0; - spin_unlock_irqrestore(&ci->lock, flags); - /* flush all endpoints */ gadget_for_each_ep(ep, gadget) { usb_ep_fifo_flush(ep); @@ -732,6 +726,12 @@ static int _gadget_stop_activity(struct usb_gadget *gadget) ci->status = NULL; }

+ spin_lock_irqsave(&ci->lock, flags); + ci->gadget.speed = USB_SPEED_UNKNOWN; + ci->remote_wakeup = 0; + ci->suspended = 0; + spin_unlock_irqrestore(&ci->lock, flags); + return 0; }

@@ -1303,6 +1303,10 @@ static int ep_disable(struct usb_ep *ep) return -EBUSY;

spin_lock_irqsave(hwep->lock, flags); + if (hwep->ci->gadget.speed == USB_SPEED_UNKNOWN) { + spin_unlock_irqrestore(hwep->lock, flags); + return 0; + }

/* only internal SW should disable ctrl endpts */

@@ -1392,6 +1396,10 @@ static int ep_queue(struct usb_ep *ep, struct usb_request *req, return -EINVAL;

spin_lock_irqsave(hwep->lock, flags); + if (hwep->ci->gadget.speed == USB_SPEED_UNKNOWN) { + spin_unlock_irqrestore(hwep->lock, flags); + return 0; + } retval = _ep_queue(ep, req, gfp_flags); spin_unlock_irqrestore(hwep->lock, flags); return retval; @@ -1415,8 +1423,8 @@ static int ep_dequeue(struct usb_ep *ep, struct usb_request *req) return -EINVAL;

spin_lock_irqsave(hwep->lock, flags); - - hw_ep_flush(hwep->ci, hwep->num, hwep->dir); + if (hwep->ci->gadget.speed != USB_SPEED_UNKNOWN) + hw_ep_flush(hwep->ci, hwep->num, hwep->dir);

list_for_each_entry_safe(node, tmpnode, &hwreq->tds, td) { dma_pool_free(hwep->td_pool, node->ptr, node->dma); @@ -1487,6 +1495,10 @@ static void ep_fifo_flush(struct usb_ep *ep) }

spin_lock_irqsave(hwep->lock, flags); + if (hwep->ci->gadget.speed == USB_SPEED_UNKNOWN) { + spin_unlock_irqrestore(hwep->lock, flags); + return; + }

hw_ep_flush(hwep->ci, hwep->num, hwep->dir);

@@ -1559,6 +1571,10 @@ static int ci_udc_wakeup(struct usb_gadget *_gadget) int ret = 0;

spin_lock_irqsave(&ci->lock, flags); + if (ci->gadget.speed == USB_SPEED_UNKNOWN) { + spin_unlock_irqrestore(&ci->lock, flags); + return 0; + } if (!ci->remote_wakeup) { ret = -EOPNOTSUPP; goto out;